1. Technical Field
The present disclosure relates to energy conversion devices especially enabling to convert thermal energy into electric signals to store this energy in electric form.
The present disclosure especially, but not exclusively, applies in the field of self-contained sensors, which are electronic devices intended to be used in locations where a simple connection to the electric supply network is not possible, or in locations where other energy sources such as solar energy have a low or no efficiency. The heat sources supplying the devices described in this embodiment may have a natural or artificial origin (fluid channeling, electronic components, Joule effect heat flow).
2. Discussion of the Related Art
The development of low-consumption electronic components, due to the miniaturization of integrated circuits, to the improvements associated with the energies require to operate them, and the widespread use of MEMS (microelectromechanical systems), inspires many developments in the exploitation of vibratory, solar, thermal, and other energies.
Many heat sources dissipate thermal energy which remains unexploited. At the same time, in certain locations of difficult access, it may be hard work or expensive to provide an electric power supply from the public distribution network or to have to perform a specific maintenance for manually recharging a battery.
It would be advantageous to be able to exploit the thermal energy where it is abundantly available, especially when other energy sources are less convenient to use.
The use of thermal energy to generate electric signals may be envisaged by several methods.
Patent DE 1184828, for example, describes an example of a system for generating current from heat by exploiting the electric permittivity variations induced by temperature variations within a ferroelectric material. The ferroelectric material is arranged between two electrodes, which results in inducing a capacitance variation between these two electrodes which follows the permittivity variations of the ferroelectric material.
One of the constraints associated with this device has to do with the availability of ferroelectric materials having Curie temperatures enabling to cover a wide temperature range to provide the current generation in various conditions, and especially close to the ambient temperature.